That’s a mystery for me too.
I’ve been working on it (to different degrees of intensity) for just over a year now, progress is accelerating fast in some ways but is complicated by the fact that I know my way around scorpion so much better so I try more ambitious stuff. Scorpion is missing a few features that I’ll need before finishing it, too.
Depending on a lot of family and health issues it’s not inconceivable I might finish making it in 2022, but I have quite a lot of real life stuff going on so fingers crossed!